Data from: Multi-electrode array for transcutaneous lumbar posterior-root stimulation

Interest in transcutaneous electrical stimulation of the lumbosacral
spinal cord is increasing in human electrophysiological and clinical
studies. The stimulation effects on lower limb muscles depend on the
depolarization of segmentally organized posterior root afferents and,
thus, the rostro-caudal stimulation site. In previous studies, selective
stimulation was achieved by varying the positions of single self-adhesive
electrodes over the thoracolumbar spine. Here, we developed a
multi-electrode surface array consisting of 3 × 8 electrode pads and
tested its stimulation-site specificity. The array was placed
longitudinally over the spine covering the T10–L2 vertebrae. Two different
hydrogel layer configurations were utilized: a single layer adhered to all
electrode pads of the array and a configuration comprised of eight
separate strips attached to the three transverse electrode pads of each
level. Voltage measurements demonstrated that an effectively focused field
distribution along the longitudinal extent of the array was not
accomplished when using the single continuous hydrogel layer, and
segmental selective stimulation of the posterior root afferents was not
possible. The separate strips produced a focused electric field
distribution at the rostro-caudal level of the electrode pads selected for
stimulation. This configuration allowed for the preferential elicitation
of posterior root-muscle reflexes in either the L2–L4 innervated
quadriceps or the L5–S2 innervated triceps surae muscle groups. Such
multi-electrode array for transcutaneous spinal cord stimulation shall
allow for improved control of stimulation conditions in
electrophysiological studies and time-dependent and site-specific
stimulation patterns for neuromodulation applications.